Abstract
PurposeRecent clinical trials showed that the sequential combination of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) and chemotherapy could prolong the PFS and/or OS of advanced non-small cell lung cancer (NSCLC) patients with EGFR mutation. The aim of present study was to assess the optimal combination sequence and to explore its possible mechanism.MethodsPC-9 cells and A549 cells, the lung adenocarcinoma cells with mutant and wide-type EGFR respectively, were treated with docetaxel/gefitinib alone or in different combination schedules. The EGFR and K-ras gene status was determined by qPCR-HRM technique. Cell proliferation was detected by MTT assay. The expression and phosphorylation of EGFR, ERK, Akt and IGF-1R were detected by western blot. Cell cycle distribution was observed by flow cytometry.ResultsOnly sequential administration of docetaxel followed by gefitinib (D→G) induced significant synergistic effect in both cell lines (Combination Index<0.9). The reverse sequence (G→D) resulted in an antagonistic interaction in both cell lines (CI>1.1), whereas the concurrent administration (D+G) showed additive (0.9<CI<1.1)-synergistic effect in PC-9 cells and antagonistic-additive effect in A549 cells. Mechanism studies showed that docetaxel-induced phosphorylation of EGFR and ERK was repressed by subsequently used gefitinib, but not by concurrent exposure of gefitinib. The gefitinib-repressed phosphorylation of EGFR and ERK was reversed neither by concurrent nor by subsequent administration of docetaxel. D+G reinforced their inhibition on the phosphorylation of IGF-1R in PC-9 cells.ConclusionsThe cytotoxic drugs followed by EGFR-TKIs may be the optimal combination for antiproliferative effects in EGFR-mutant NSCLC cells, and the phosphorylation of EGFR and ERK might contribute to this effect.
Highlights
Non-small cell lung cancer (NSCLC) is the leading cause of cancer death worldwide
The cytotoxic drugs followed by EGFR-TKIs may be the optimal combination for antiproliferative effects in EGFR-mutant NSCLC cells, and the phosphorylation of EGFR and ERK might contribute to this effect
EGFR and K-ras gene status in A549 and PC-9 cell lines qPCR-HRM technique showed that A549 cells harbored a mutation in K-ras exons 2 and no mutation in EGFR gene
Summary
It is well known that for treatment of advanced NSCLC, epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) and chemotherapy is recommended as first-line therapy for patients with active EGFR mutation and wild type EGFR, respectively. This recommendation is based on the results of a phase III randomized trial IPASS in which patients with EGFR mutations who received gefitinib had increased progression-free survival (PFS 24.9% vs 6.7%), response rate (RR 71.2% vs 47.3%) and quality of life when compared with those receiving chemotherapy [1]. We presumed that further improvements might come from the findings of new target, the overcoming of EGFR-TKIs tolerance and the combination of EGFR-TKI with chemotherapy since the mechanisms of their anti-tumor activity are different
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